osPID as a composite bonder

[idmcb]

#3618

So I came across the osPID in my search to supplement some equipment I have to perform hot bonds on aviation composite structures. The traditional hot bonders use an AC driven heating element in the 1500-2000 watt range, embedded in silicone, to warm thermosetting resins to the point of cure. The cycle usually takes this form: under vacuum, a ramp from ambient temp to either an intermediate temp (150 degrees F) or a final temp (normally 250 degrees, but some advanced materials can go as high as 500), a period soak, and then a ramp down back to ambient. The java interface looks like it will record the information that I’d need to see. OK; so nothing so far that the PID cannot do. What it would need to do in addition is monitor a vacuum source for a low threshold and trigger an alarm if vacuum is lost (which I think it can) and utilize more than one high temp thermocouple. Most systems in use sum three and start a soak period once the low thermocouple reaches target. Maybe trigger another alarm if a thermocouple is lost during process, and discontinue cure if temp exceeds a threshold as a fire hazard preventative thing. I’ve looked at arduino before and the 1-wire digital temp sensors can be ganged for a similar application, but I haven’t found any that can be utilized in the variety of temps that I’d need. The digital ones just won’t survive a 250+ degree environment. Any ideas? I’m really itching to try the osPID but I am new to the arduino platform and nervous about jumping in to a development project that is over my head.

MB

[Brett]

#4045

I think you could probably cram all the hardware in there, but a decent amount of custom work would need to be done for the osPID to fit your application. because the application is slow, you could probably use 2 digital pins to cycle through the termocouples, having them share a single input. that would leave room for your pressure sensor. from a form-factor perspective though, I’m not sure if everything would fit. 4 sensors= 8 terminal connections. the standard osPID terminal block only has 6, so you’d need to find a 8 screw block that would fit in the same space.

this says nothing about the firmware / software changes that would be needed. on the firmware, you’d need to add the thermocouple switching code, as well as some alarming stuff, and on the software side there would need to be input fields for the alarm points, as well as more trends added for the multiple inputs.

My assessment is that the current osPID can’t do it. if you’re looking for a one-off, the amount of time it would take to make would make it more expensive than a professional unit. IF, however, there was a big enough market for this, there might be economic justification for someone to run with this and make/sell a custom solution. as long as that’s open source, we’d have no issues with that.

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